Multiresonator magnetron



April 3,1951 SMITH 2,547,503

MULTIRESONATOR MAGNETRON 2 Sheets-Sheet 1 Filed Nov. 9, 1945 Isnnentor PmuT. 5mm

April 3, 1951 P. T. SMITH 2,547,503

MULTIRESONATOR MAGNETRON Filed Nov. 9, 1943 I 2 Sheets-sheet 2 INVENTOR PHILIP T. SMITH wwww ATTORN EY Patented'Apr. 3, 1951 MULTIRESONATOR MAGNETRON Philip T. Smith, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application November 19, 1943, Serial No. 510,871

12 Claims.

My invention relates to electron discharge devices and associated circuits useful at ultra high frequencies and more particularly to magnetrons utilizing cavity resonator circuits.

In certain types of magnetrons the anode segments are inter-connected by means of cavity resonator circuits and form together the anode structure for the magnetrons. The usual construction comprises an elongated centrally positioned cathode having an anode member surrounding the cathode. In one form of magnetron, the anode member is provided with a plurality of cavity resonator circuits formed by cylindrical cavities in the anode member, slots extending between these cavities and the space between the cathode and the anode member, the anode segments being formed by the portions of the anode member positioned between adjacent slots, the slots lying parallel to the cathode.

In any multiple cavity resonator magnetron the cavities must of necessity have a finite length. Consequently, end effects are encountered which may be incompatible with the desired electromagnetic field within the main part of the magnetron itself. That is, a number of possible modes of operation will exist, some of which are associated with difierent frequencies and some of which are degenerate; for example, in a twelveslot anode magnetron it is possible to have eleven different modes of operation and six distinct frequencies, the mode associated with the highest frequencies being non-degenerative while all other modes are degenerative. Since all six frequencies lie so near one another, frequency instability may develop under load. Because of the small difference between frequencies it is difiicult to confine the generation of 'power to just one of the modes.

I The object of my invention is to provide an electron discharge device of the magnetron type of improved design.

Another object of my invention is to provide tion itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a top view with portions removed to show details of construction of an electron discharge device and associated circuit made according to my invention, Figure 2 is a bottom View with parts removed to show details of construction of the device shown in Figure 1, Figure 3 is a longitudinalsection taken along the line 3-3 of Figure 1, Figure 4 shows a detail of the coupling loop used with an electron discharge device made according to my invention, Figure 5 is an enlarged section showing details of construction of a device made according to my invention, Figure 6 is a developed view of a portion of the anode assembly showing details of construction of an electron discharge device made according to my invention, and Figures l, 8vand such a device utilizing cavity resonators in which only the desired electromagnetic fields within the main part of the magnetron itself are produced.

9 show different forms of plate members from which the anode assembly is made according to my invention.

As best shown in Figures 1 to 3 inclusive, an electron discharge device made according to my invention includes a preferably indirectly heated cathode it, surrounded by an anode assembly I 1, comprising stacked plate members to be described in greater detail below. Mounted at the top and bottom of this assembly are the cup-shaped elements l2 and i3 forming part of the envelope and sealed vacuum tight to the assembly. All of the parts may be silver soldered together. The cathode is supported by means of the bracket members, for example, [6 and H, which may be secured to the cup-shaped members I2 and [3, which in turn support the bridging structure comprising the insulating elements [8 and I9, which in turn support the strap elements 19" on which the cathode is secured by means of the disc elements 20. The disc elements 2! serve as electron shields to prevent stray electrons from leaving the cathode-anode space and as a heat shield. The ends of the cup-shaped members are sealed by means of the cup-shaped elements it and 15 and a magnetic field is provided by means of the electromagnetic members 22 and 23. Cathode heater current is brought to the cathode heater by means of leads 24, 25 extending through the cup-shaped member l2 and sealed through the wall of the envelope by means of the cup-shaped member 26.

The details of the cathode support and heater wires are shown in Figure 5.

In accordance with my invention stacked plates make up the anode assembly comprising the intermediate elements 39 shown in Figure 9, the end elements 3| shown in Figure 8 and the closure members 32 shown in Figure 7. It will be noted that the intermediate plate members 30 are provided with a plurality of pairs of parallel shots, such as 33 and 34, providing the intermediate finger element 34, the slots opening into the center opening 36] for receiving the cathode. Each end plate member 3| has a plurality of slots 35 opening into the central opening 3i for receiving the cathode. The slots 35 are in width equal to the space between the outer edges of the slots 33 and 34. The closure members 32 are provided only with the center cathode opening 32. These disc-like elements are assembled in the manner shown in Figure 6 so that a plurality of radially extending anode elements with slots in between are provided, alternate elements being spaced at the top and bottom from the closure members 32. It will thus be seen that in effect the central portion made up of the fingers 315" provides the middle conductor of a rectangularly shaped coaxial line cavity resonator open only at the inner end adjacent the cathodeanode' space and closed at the opposite end and at the sides. The eilect of this is to confine the electromagnetic field within coaxial line cavity resonators and provide a uniform field consistent with the desired field for efiicient operation. The various resonators are coupled together electrically and electromagnetically within the oathode anode region:

Although the slots 33 and 34 are shown as parallel slots, the slots may be radial. However, withparallel slots the radial distance around the inner conductor of each resonator is constant which is a desirable feature.

The-plates'from which the anode assembly and resonators aremade may be punched copper laminations silver soldered together. This ma be done by means or thin sheets of suitable solder or silver plating the laminations. It it obvious that the cavities forming the resonators may be machined or broached out of solid copper and the end platessoldered to the block.

Power is taken out of the oscillator by any suitable means; for example, the coaxial line coupling means shown in Figure 4 in which the inner conductor d6 extends through the cupshaped closure member I3 and is surrounded by I the outer conductor ii, continued outside the envelope at 43 and sealed oh by insulating cupshaped element 53. The inner conductor passes through a' small aperture 42 in the closure plate 32 and is connected to the end one of plates 35,

to couple with the spacein one of the coaxial line resonators.

- While I have indicated the preferred embodiments'of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, itwill beapparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may bemadein the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is:

1. An electron discharge device including an elongated cathode and an anode member surrounding said cathode, said anode member having a central space around said cathode and a plurality of pairs of adjacent slots communicatingwith said space, the-slots of each pair being parallel to each other, each pair of parallel slots having communicating passageways therebetween at the extremities thereof, said slots and passageways providing radially directed coaxial line resonators, and means for producing a magnetic field parallel to said cathode and between said cathode and said anode member.

2. An electron discharge device including an elongated. cathode and. an anode member surrounding said cathode, said anode member having a central space around said cathode and a plurality of pairs of slots communicating with saidspace, the slots of each pair being parallel to each other, each pair of parallel slots having communicating passageways therebetween at the extremities thereof, said slots and passageways providing radially directed coaxial line resonators, and means for producing a magnetic field parallel to said cathode and between said cathode and said anode member, said slots extending axially of said cathode whereby said resonators have an elongated transverse rectangular shape.

3. An electron discharge device having an elongated cathode, a cylindrically shaped member surrounding and coaxial with said cathode and comprising a plurality of stacked plate-like elements extending transversely of said cathode, conducting means contacting the ends of said cylindrically shaped member and enclosing the space between said plate-like elements and the cathode, the plate-like elements positioned between said conducting means having eiongated tooth-like portions extending toward said cathode and forming with said first conducting means a plurality of coaxial line resonators, the open ends of which are adjacent said cathode, and means for providing a magnetic field parallel to said cathode and between said cathode and said platelike elements.

4. An electron discharge device including an elongated cathode and an anode member surrounding said cathode, said anode member having a central space around said cathode and a plurality of 'pairs of axially extending adjacent paraliel slots communicating'with said space, alternate portions ofsaid anode member intermediate said slots being of shorter axial length than the other portions intermediate the slots, and closure members contacting the top and bottom of said anode member, whereby spaces are formed between the ends of the shorter portions and the closure members to provide coaxial line resonators, and means for producing a magnetic field parallel to said cathode and between said cathode and said anode member.

5. An electron discharge device having an elongated cathode and surrounded by an anode assembly comprising a plurality of stacked, punched discs, the intermediate discs including. a plurality of radially extending pairs of adjacent slots; a disc at each end of said assembly having radially extending slots of greater width than the slots in said intermediate discs, the edges of each slot in said end discs registering with the outer edges of a pair of slots in said intermediate discs, and a closuremember at the' ends of said anode assembly closing the space between the cathode and said stacked discs, and means for producing a magnetic field parallelto said cathode and between said cathode and anode assembly.

6. An electron discharge device having an elongated cathode and surrounded by an anode assembly comprising a plurality of stacked,

punched discs, the intermediate discs including a plurality of radially extending pairs of adjacent slots, a disc at each end of said assembly having radially extending slots of greater width than the slots in said intermediate discs, the edges of each slot in said end discs registering with the outer edges of a pair of slots in said intermediate discs, and a closure member at the ends of said anode assembly closing the space between the cathode and said stacked discs, and means for producing a magnetic field parallel to said cathode and between said cathode and anode assembly, and a coupling loop extending through a closure member and a slot of greater width and contacting the portion between a pair of slots oi an intermediate disc.

7. An electron discharge device having an elongated cathode, an anode member surrounding said cathode and having formed therein a plurality of coaxial line resonators spaced around said cathode and extending outwardly from said cathode, each of said coaxial line resonators having an open end adjacent the cathode and a closed end remote therefrom, and a cup-shaped member positioned at each end of the anode member and sealed thereto, and a bridging member within said cup-shaped member insulatingly supporting the cathode within the anode member, and a closure member for each of said cup-shaped members providing a vacuum-tight envelope for said cathode, and means for producing a magnetic field parallel to said cathode and between said cathode and said anode member.

8. An electron discharge device having an elongated cathode and surrounded by an anode assembly comprising a plurality of stacked, punched discs, intermediate discs having a plurality of radially extending pairs of adjacent slots, a disc at each end of said assembly havin radially extending slots of greater width than slots in said intermediatediscs, the edges or" each slot in said end discs registering with the outer edges of a pair of slots in said intermediate discs, and a closure member at the ends of said anode assembly closing the space between the anode and said stacked discs, and cup-shaped members sealed to said closure members and having means insulatingly supporting the cathode with respect to said anode assembly, and closure members for said cup-shaped members providing a vacuumtight envelope for said cathode, and means for producing a magnetic field parallel to said cathode and between said cathode and anode assembly.

9. An electron discharge device including an means for producing a magnetic field parallel to said cathode and between said cathode and said anode member.

10. An electron discharge device including an elongated cathode and an anode member surrounding said cathode, said anode member ha"- ing a central space around said cathode and a plurality of pairs of adjacent slots communicating with said space, adjacent slots having communicating passageways therebetween in pairs at the extremities thereof, the adjacent slots of different pairs being unconnected at their extremities, said slots and passageways providing radially-directed coaxial line resonators, and means for producing a magnetic field parallel to said cathode and between said cathode and said anode member.

11. An electron discharge device including an elongated cathode, an anode member surrounding said cathode and having formed therein a central space around said cathode and a multiplicity of coaxial line resonators spaced around said space and extending outwardly therefrom, conducting means interposed between adjacent coaxial line resonators preventing electromagnetic coupling therebetween except through said space each or" said coaxial line resonators having an open end adjacent said space and a closed end remote therefrom, said coaxial line resonators being elongated transversely thereof in a direction parallel to said cathode, and means for producing a magnetic field parallel to said cathode and between said cathode and said coaxial line reso- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,034,034 Green et a1 Mar. 1'7, 1936 2,034,036 Green Mar. 17, 1936 2,115,521 Fritz et a1. Apr. 26, 1938 2,190,511 Cage Feb. 13, 1940 2,266,428 Litton Dec. 16, 1941 2,287,845 Varian June 30, 1942 2,404,212 Bondley July 16, 1946 2,419,172 Smith Apr. 15, 1947 2,446,825 Gurewitsch Aug. 10, 1948 2,458,802 Spencer Jan. 11, 1949 

